The LEAFY (LFY) homologous gene of Dendrobium moniliforme (L.) Sw. was cloned by new primers which were designed based on the conservative region of known sequences of orchid LEAFY gene. Partial LFY homologous gene was cloned by common PCR, then we got the complete LFY homologous gene Den LFY by Tail-PCR. The complete sequence of DenLFY gene was 3 575 bp which contained three exons and two introns. Using BLAST method, comparison analysis among the exon of LFY homologous gene indicted that the DenLFY gene had high identity with orchids LFY homologous, including the related fragment of PhalLFY (84%) in Phalaenopsis hybrid cultivar, LFY homologous gene in Oncidium (90%) and in other orchid (over 80%). Using MP analysis, Dendrobium is found to be the sister to Oncidium and Phalaenopsis. Homologous analysis demonstrated that the C-terminal amino acids were highly conserved. When the exons and introns were separately considered, exons and the sequence of amino acid were good markers for the function research of DenLFY gene. The second intron can be used in authentication research of Dendrobium based on the length polymorphism between Dendrobium moniliforme and Dendrobium officinale.

Simple sequence repeat (SSR) was used to investigate the genetic diversity and structure of Dendrobium officinale. A total of 15 primer pairs with stable and repeatable polymorphism were screened out from 60 SSR primer pairs developed by the method of microsatellite enrichment by magnetic beads. Forty-eight samples of Dendrobium officinale were analyzed in genetic polymorphism. These loci were polymorphic and displayed 3 to 9 alleles per locus with a mean number of 6.1. The observed and expected heterozygosities ranged from 0.60 to 0.85 and from 0.49 to 0.85 respectively. The polymorphic information content (PIC) of each SSR locus varied from 0.437 to 0.829 with an average of 0.702. Fifteen primer pairs were used in Dendrobium cross-species amplification and totally 13 primer pairs were proved to have the transferability in D. officinale related species. In addition, 500 tissue culture plantlets of D. officinale were tested for purity identification by means of PCR amplification with four SSR primer pairs. The results showed that SSR technique is a feasible, simple and inexpensive method for determining adulterants in germplasm identification.

Random amplified microsatellite polymorphism (RAMP) markers were used to access the genetic diversity among 112 samples of nine populations of Dendrobium officinale Kimura et Migo. Using 16 informative primers, 123 bands were amplified and 86 (69.92%) were polymorphic. The polymorphic bands from three to eight could be detected for each RAMP primer, with a mean of 5, indicating abundant genetic diversity among populations. Genetic similarity coefficients ranged from 0.250 to 0.813. UPGMA dendrogram illustrated 9 populations clustered into 3 groups, and the cluster pattern showed correlation with the locations of the D. officinale populations. These results were supported by the previous conclusions that were achieved by other molecular markers, and RAMP is proved to be effective for evaluating the genetic diversity of wild populations of Dendrobium officinale.

To identify adulterants from medicinal plants of Bletilla H. G. Reichenbach, the suitable candidate DNA barcoding of Bletilla was evaluated. In this study, the internal transcribed spacer (ITS) of nuclear ribosomal DNA, the LFY homologous gene intron 2 and chloroplast ycfl gene were amplified and sequenced from forty-one samples. The intra-specific and inter-specific divergences of Bletilla were calculated, and the identification efficiency was assessed using Barcoding Gap, NJ tree by K2P distance and BLAST1 method. The result showed the intra-specific divergence of nrDNA ITS and ycJfl (0.022-0.106 and 0.017-0.106) were obviously higher than the inter-specific divergence (0-0.012 and 0-0.015), and four species of Bletilla were also accurately distinguished in NJ trees. Whereas, there was no Barcoding Gap on LFY homologous gene intron 2, thus it cannot effectively identify species of Bletilla. Using NJ tree of nrDNA ITS and ycfl gene, powdery medicine and the adulterants of Bletilla were successfully unidentified. In conclusion, nrDNA ITS and ycfl can be used as a potential DNA barcoding to identify the medicinal plants in Bletilla and its adulterants. There were only three basic differences on nrDNA ITS between "Jujing baiji" and Bletilla striata of Lu'an in Anhui province, and two basic differences in ycfl. Based on morphological and molecular data, "Jujing baiji" could be recognized as the species of Bletilla striata.

Bletilla striata has been used as traditional Chinese medicine for several centuries. In recent years, the quality and quantity of wild B. striata plants have declined sharply due to habitat deterioration and human over-exploitation. Therefore, it is of great urgency to evaluate and protect B. striata wild plant resource. In this study, sequence-related amplified polymorphism (SRAP) markers were applied to assess the level and pattern of genetic diversity in twelve populations of B. striata. The results showed a high level of genetic diversity (PPB = 90.48%, H = 0.349 4, I = 0.509 6) and moderate genetic differentiation among populations (G(st) = 0.260 9). Based on the unweighted pair-group method with arithmetic average (UPGMA), twelve populations gathered in three clusters. The cluster 1 included four populations. There are Nanjing, Zhenjiang, Xuancheng and Hangzhou. The seven populations which come from Hubei Province, Hunan Province, Jiangxi Province and Guizhou Province belonged to the cluster 2. The cluster 3 only contained Wenshan population. Moreover, Mantel test revealed significant positive correlation between genetic distances and geographic distances (r = 0.632 9; P < 0.000 1). According to the results, we proposed a series of conservation consideration for B. striata.